This invention relates to drop-on-demand ink jet print heads and in particular to a high-performance, print media-width plate stacked print head incorporating multiple arrays of ink jets that are optimized for purgability, jetting uniformity, and high drop-ejection rate performance. More specifically, the invention is directed to a plurality of acoustic filters formed and imbedded in the ink jet head to suppress unwanted frequencies that may arise during different print modes.
There are well-known apparatuses and methods for implementing multiple-orifice drop-on-demand ink jet print heads. In general, each ink jet of a multiple-orifice drop-on-demand ink jet array print head operates by the displacement of ink in an ink pressure chamber and the subsequent ejection of ink droplets from an associated orifice. Ink is supplied from a common ink supply manifold through an ink inlet to the ink pressure chamber. A driver mechanism is used to displace the ink in the ink pressure chamber. The driver mechanism typically includes a piezoelectric transducer bonded to a thin diaphragm. When a voltage is applied to the transducer, it displaces ink in the ink pressure chamber, causing the ink to flow through the inlet from the ink manifold to the ink pressure chamber and through an outlet and passageway to the orifice.
It is desirable to employ a geometry that permits the multiple orifices to be positioned in a densely packed array. Suitably arranging the manifolds, inlets, pressure chambers, and the fluidic couplings of the chambers to associated orifices is not a straightforward task, especially when compact ink jet array print heads are sought. Incorrect design choices, even in minor features, can cause nonuniform jetting performance. Uniform jetting performance is generally accomplished by making the various features of each ink jet array channel substantially identical. Uniform jetting also depends on each channel being free of air, contaminants, and internally generated gas bubbles that can form in the print head and interfere with jetting performance. Therefore, the various features of the multiple-orifice print head must also be designed for effective purging. Also described is the effect of pressure chamber resonances on jetting uniformity and the use of dummy channels and compliant wall structures to reduce reflected wave-induced cross-talk in a 36-orifice ink jet print head.
Prior art print heads are typically constructed of laminated plates that together form associated arrays of ink manifolds, diaphragms, ink pressure chambers, ink inlets, offset channels, and orifices. Particular plates also form black, yellow, magenta, and cyan ink manifolds that are distributed elevationally above and below the other internal ink jet features. In particular, the elevationally lower manifolds are connected to the upper manifolds by ink communication channels. Moreover, the tapering and sizing of the manifolds and other internal ink jet features minimizes cross-talk and resonance-induced jetting nonuniformities. Additionally, various print modes result in unwanted frequencies that can span several orders of magnitude. These frequencies result in print artifacts normal to the direction of printing. Also, the highest unwanted frequency causing such affect is induced in the system is the actuation frequency of the single jets.
Accordingly, this invention provides acoustic filters for use in an ink jet print head. The ink jet print head defines a plurality of operating plates held together in a superimposed relationship forming an ink jet print head defining a plurality of ink manifolds, ink inlets, ink drop-forming orifices and a plurality of acoustic filters. The acoustic filters are a plurality of compliant areas connected by an acoustic filter constriction aperture and a plurality of separate compliant areas all connected to ink manifolds for suppressing unwanted frequencies during print modes.
Additional objects and advantages of this invention will be apparent from the following detailed description of a preferred embodiment thereof that proceeds with reference to the accompanying drawings.